By no means an expert here, just some more interested Googling...
1. Have you tried it on a standalone 'buntu or some other system? I wonder if it's an issue with firmware as bundled with OE:
http://askubuntu.com/questions/308695/help-with-hauppauge-wintv-hvr-2250-on-ubuntu-13-04
2. Have you tried stopping and restarting tvheadend? It may be a timing issue if the tuner is initialising slowly.
3. Are you looking at the right tuners? I've never seen a /dev/videoX device on my tvheadend systems - only ever /dev/dvb/adapterX. Are the Samsung tuners listed genuinely different tuners, or is the card presenting multiple faces to the OS? If the Samsung chips are in the 2250, can you get services/channels on those? I wonder if the /dev/video devices are analogue, or some other input that tvheadend doesn't like even if the OS is okay with them - but it could be an ASTC artefact as well.